During conventional data transmission between memory and a System on Chip (SoC) that sends and receives data, the component that reads data does so by reading a data signal along a data line. The component reads the data signal upon receiving a strobe signal, which defines the timing at which to read the data signal. More specifically, the component reads the data signal along the data line upon detecting the rising edge of the strobe signal.
As shown in FIG. 15, an SoC 1500 and memory 1501 are connected by a data line and a strobe line. If the timing at which data is on the data line becomes misaligned from the rising of the strobe signal, data cannot be read correctly. To allow for some fluctuation in the rising edge of the strobe signal, delay adjustment is therefore necessary to set the strobe signal to rise in the middle of the period when the data signal is on the data line. In other words, in FIG. 15, it is necessary to delay the strobe signal so that, while the data signal is on the data line, the rising edge of the strobe signal coincides with the delay E. Note that the term “delay” refers to the length of time from when the data signal is first transmitted on the data line until the rising of the strobe signal.
During delay adjustment, when the SoC 1500 itself outputs data, the rising of the strobe signal should be aligned with the middle of the period when the data is on the data line. To achieve this alignment, the SoC 1500 can output a data signal and a strobe signal to the memory 1201 synchronously, while causing only the strobe signal to pass through a prescribed number of delay elements located in the SoC 1500.
On the other hand, the memory 1501 can only align the start and the duration of output of a data signal with the rising edge and falling edge of a strobe signal. Accordingly, the SoC 1500 itself has to delay a strobe signal received from the memory 1501, detect the rise of the strobe signal thus delayed, and then read data. Delay adjustment refers to determining how much to delay the strobe signal and then delaying the strobe signal by the determined amount.
Patent Literature 1 discloses a device that performs delay adjustment at the time of system startup or system reset.